Combine flour, pistachios, sugar and salt in a food processor. Process until the pistachios are relatively fine.

Cut butter into large chunks and add to food processor. Whiz for about 1 minute, until dough has a very sandy texture and starts to clump together. Pour into a 9-inch square pan and spread into an even layer. Aim for a smooth surface. If you have a fancypants shortbread pan like I do, you should use it.

Score dough lightly with a knife, marking 4 rows by 8 rows of shortbread pieces (unless you’re baking it in the shorbread pan). Dock the dough with a fork.

Bake for 30-35 minutes, until shortbread is lightly browned all over.

While the shortbread is still hot, use a sharp knife to cut shortbread all the way through along the lines you scored prior to baking. Allow shortbread to cool completely once it has been cut.

If you want to make some icing, mix icing sugar with enough milk (or rosewater) to make a smooth paste. Loose enough to drizzle, but firm enough to hold it’s shape. I never measure. Just go by feel, it’ll be fine.

When cool, shortbread pieces should break apart very easily. Store in an airtight container.